Recently Mike Grehan interviewed Jon Glick, who is Yahoo!'s Senior Manager for Web Search. You can read all the good Yahoo! Search stuff (note to self: stuff is a generic word to use in anchor text) in it, or look at my synopsis below. Yahoo! Search
How was Yahoo! Search Made?

The goal in creating Yahoo! search technology was not, you know, let's take a piece here a piece there...AllTheWeb was very, very good at was rebuilding indexes and keeping very high levels of freshness...Alta Vista had a really good core technology called MLR (machine learn ranking).

The best of breed parts of those engines were included with some of the best parts of Inktomi to make the new Yahoo! Search.

Meta Keywords
How is Yahoo! Search using the meta keywords tag?

Each keyword is an individual token separated by commas...For best practice you just need to remember it's for matching - not ranking...‘laptop computers’ will count for ‘laptop computers’ and not ‘laptop’ or ‘computers’ separately.

Essentially this is a good place for synonyms & misspellings (I tend to have some of them in my copy anyway)...Each keyword phrase is unique and separated by commas, so you will not have set off a flag for laptops if you use a meta tag such as
<meta name="keywords" content="Yahoo! laptops, computer laptops, compaqt laptops, compak laptops">

but you will also want to get words such as "lap tops" and "compaqt lap tops" in your meta tags. Each version helps to get your file included in that specific subset of search results, but has no influence on rankings.

Meta Description
How does Yahoo! Search use the meta description tag>

Yes we do use meta keywords. So let me touch on meta tags real fast. We index the meta description tag. It counts similar to body text.

Page Title Tag
How should I write my page title tag?

The title tag? My biggest recommendation is write that for users! Because that's the one real piece of editorial in the search listing that you can absolutely control...We typically show, roughly 60 characters. That's the maximum we'd show. I'm not a professional copywriter, so I can't tell you "is short and punchy better than lots of information..."

Affiliate Marketing
Why does Yahoo! hate affiliate marketers?

Well let me just say first that, in that sense Spam has gotten a lot better over the years. You don't really much have people trying to appear for off topic terms as they tended to. You now have people who are trying to be very relevant. They're trying to offer a service, but the issue with affiliate Spam is that they're trying to offer the same service as three hundred other people.